1. Field of the Invention
The present invention relates to an inkjet head that performs recording by discharging ink to a recording surface of a recording medium. In particular, the present invention relates to an inkjet head including supply ports that extend through a recording element substrate and an orifice plate stacked on the recording element substrate.
2. Description of the Related Art
An inkjet recording apparatus, which uses a non-impact recording method, has advantages of making little noise during recording and performing high-speed and high-resolution recording on various recording media. Examples of the inkjet recording apparatus include the apparatus having such characteristics described in U.S. Pat. No. 6,863,381. The document discloses a configuration in which nozzle arrays for discharging ink are each disposed on one side of a corresponding supply port (ink via) on a recording element substrate (heater chip), and the distances from longitudinal edges of outermost supply ports to edges of the recording element substrate are different.
In recent years, recording element substrates have been becoming smaller as printers and the inkjet heads have been miniaturized for cost reduction. U.S. Pat. No. 6,863,381 proposes a configuration in which nozzle channels, which had previously been formed on both sides of each of the supply ports, are disposed on one side of each of the supply ports with higher density. This serves to save space at the unused sides and downsize the recording element substrate.
When a recording element substrate having an orifice plate stacked thereon is bonded to a resin inkjet head member with a thermosetting adhesive, a compressive stress is applied to the recording element substrate at normal temperature, because a resin generally has a larger linear expansion coefficient than a metal that composes the recording element substrate.
FIG. 8 shows a schematic view of an inkjet head disclosed in U.S. Pat. No. 6,863,381. As shown in the figure, if the compressively-stressed part of the recording element substrate has a low rigidity, the orifice plate is deformed together with the recording element substrate 1. Thus, ground areas (hereinafter also referred to as channel walls), which connect the orifice plate and the recording element substrate so as to form ink channels, may become unstuck. In an area where ink channels are formed between an edge of the recording element substrate 1 and a supply port, a driving circuit and wiring for energy generating elements are disposed. Because downsizing is difficult for such a part, this part serves to ensure sufficient width and rigidity near the edge of the recording element substrate 1.
FIG. 9 shows a configuration of an inkjet head disclosed in U.S. Pat. No. 6,863,381. In FIG. 9, three supply ports 30, 40, and 50 are provided. Energy generating elements H10, H20, and H30 are arranged at the respective supply ports 30, 40, and 50. In the configuration disclosed in U.S. Pat. No. 6,863,381, as shown in FIG. 9, the distances from edges of a recording element substrate 1 to the supply ports nearest to the edges (supply ports 50 and 30) are different for different edges. As shown in FIG. 8, ink channels are not formed in an area between a supply port and an edge of the recording element substrate at one edge of the substrate (the right edge of the recording element substrate in FIGS. 8 and 9). When this area is too small, rigidity of the area may be low and channel walls may become unstuck.